Search

Soybean production can be affected by heat (HS) and water stress (WS). However, studies on effects of stresses combination under field conditions are still scarce. The objective of this study was to evaluate the impact of HS, WS and their interaction (HS × WS) during seed filling on seed weight, seed growth rate (SGR) and seed filling duration (SFD) of same phenological age pods from different canopy positions. Two soybean genotypes were exposed to four treatments during seed filling: control (irrigated plots at ambient temperature), HS (plots under temperatures >32°C for 6 hr/day during 15 days), WS (plots under 25% of soil water content, during entire seed filling) and HS × WS. Stresses interaction caused similar responses to WS alone, decreasing yield and its components (seed number and weight), as well as seed weight for each canopy position (SWCP), SGR and SFD. Non‐significant effect of irrigated HS and non‐additive effects was observed in HS × WS plots, exhibiting WS a dominant effect over HS. The SWCP strongly correlated with SGR, exhibiting upper position a trend to higher SWCP than lower one. Seed maximum water content and pod weight, positively associated with SWCP, indicated seed metabolic limitations under WS and HS × WS. Our results advance in the understanding of SW determination under abiotic stresses and highlight the importance of identifying pods of same phenological age to establish accurate comparisons between seeds from different canopy positions. [ABSTRACT FROM AUTHOR]

Copyright of Agronomía & Ambiente is the property of Universidad de Buenos Aires. Facultad de Agronomia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wheat crop response to sulfur (S) depends on nitrogen (N) level, genotype and environmental conditions, demonstrating strong genotype×environment×nutrients interactions. The agronomic-use efficiency of both nutrients has not been evaluated in a wide range of modern genotypes differing in their cycle length and baking quality. The aim of this study was to analyse the effect of Nand S fertilisation on yield components and use efficiency of both nutrients in 24 modern, high-yielding bread wheat genotypes (including long and short crop cycles) grown in contrasting environments in the Humid Pampa of Argentina. Two experiments were conducted under contrasting seasonal conditions on a Mollisol in Azul, Buenos Aires. Significant effects of N (range 15-200 kg N ha-1) on grain yield were observed in all genotypes. By contrast, responses to S (30-100 kg S ha-1) were found only at high N level in low soil-fertility environments, differing between long and short cycles. Genotype×fertilisation interaction was significant in the environment with higher soil fertility. Sulfur addition improved N-recovery efficiency (0.15 v. 0.32) and agronomic efficiency of the available N (84 v. 93 g g-1) in the poor-fertility environment, characterised by their N and S deficiency and moderate level of organic matter. Grain N-recovery efficiency was largely explained by increases in grain number, whereas S recovery was also associated with increases in grain nutrient concentration. We conclude that genotype and environment strongly alter fertiliser-use efficiency, providing valuable information for ranking genotypes and optimising site-specific management of wheat crops in the Humid Pampa of Argentina. Grain S percentage may be useful as a physiological marker for selection of bread wheat genotypes with high apparent S recovery. [ABSTRACT FROM AUTHOR]

Wheat is a crop of vital importance for food security. In contrast to the accumulated knowledge for yield determination, the effect of variations in the source/sink (S/S) ratio on grain quality, and its interaction with the genotype and fertilization level, have received little attention. This work aimed to analyze the incidence of S/S ratio changes during post-flowering on grain weight and commercial quality in bread wheat genotypes with contrasting baking aptitude, as well as to evaluate its interaction with early nitrogen-sulfur fertilization. It is hypothesized that modern wheat genotypes bred for high-yield and contrasting baking aptitudes differ in their responses to variations in the availability of assimilates during post-flowering. Rainfed field trials were carried out in the Humid Pampas of Argentina during two years. Six wheat genotypes belonging to different quality groups were used, to which manipulative S/S treatments in post-flowering (shading, defoliation, thinning, trimming) and different levels of nitrogen-sulfur fertilization were applied. Regressions between S/S ratio (growth per grain) and grain variables (grain weight, protein content per grain, protein concentration, and test weight) were analyzed. Grain weight responses ranged from − 42% to + 31% relative to control compared to variations in S/S ratio from − 81% to + 56%, varying with the year and genotype. Relative changes of grain weight and S/S ratio were linearly associated, showing differences in stability (slope range: 0.29–0.80) among genotypes (the lower the slope, the greater the stability). Protein content per grain increased linearly with increases in the S/S relationship only for fertilized crops with N and S. As expected, protein concentration decreased when the S/S ratio increased, while test weight was the opposite. Importantly, responses varied among genotypes and fertilization levels, regardless of baking quality group. Grain weight to S/S ratio after flowering relationships differed between bread wheat genotypes, even within the same quality group, while protein content stability did not differ significantly. Therefore, for the conditions of this study in high-yielding environments in the Humid Pampas, the different protein concentration responses were due to genotypic differences in grain weight stability against variations in assimilates availability during grain filling. Nitrogen-sulfur fertilization early at the crop cycle did not modify the grain weight responses to variations in the S/S ratio, although it increased their influence on the commercial quality parameters. These findings are relevant to genetic improvement for high yield that can increase the co-limitation by source and sinks, and the occurrence of farm adversities that restrict the source capacity during post-flowering. • The impact of source/sink ratio on wheat grain weight and their quality were assessed. • Genotypes differed in their grain weight stability to source/sink ratio changes. • Test weight was more stable for genotypes with the best baking quality. • N-S fertilization increased responses of protein percentage and test weight to source/sink ratio. [ABSTRACT FROM AUTHOR]